Biology Chapter 2: Molecular Components of Cells

Chapter 2: Molecular Components of Cells

• Lipids are non-polar, insoluble in water, but soluble in non-polar solvents.
• Lipids have various functions, including structural roles (phospholipids in cell membranes), energy storage (triglycerides), and communication (steroids, hormones, eicosanoids).
• Phospholipids are a component of cell membranes.
• Triglycerides are stored in plant seeds and animal adipose tissue.
• Steroid hormones, eicosanoids, and phosphatidylinositol are all types of lipids involved in communication.

Lipids: Types

• Saponifiable lipids have fatty acids (f.a.) and can undergo saponification (reaction with a strong base).
• Non-saponifiable lipids do not contain fatty acids.

Saponification

• Saponification is a reaction between a glyceride (fat) and KOH (potassium hydroxide) to form glycerol and soap (potassium salts of fatty acids).

Saponifiable Lipids: Fatty Acids

• Fatty acids are amphipathic (having a polar hydrophilic head and a nonpolar hydrophobic tail).
• The formula of a fatty acid is CH3-(CH2)n-COOH (where 2 ≤ n ≤ 20).
• The value of 'n' is always even.
• Fatty acids are more energetic than carbohydrates.
• Fatty acids differ by length and saturation (degree of unsaturation), influencing membrane fluidity.
• Saturated fatty acids have no double bonds, whereas unsaturated fatty acids have one or more.
• Saturated fatty acids are solid at room temperature, while unsaturated fatty acids are fluid at room temperature.

Saponifiable Lipids: Triglycerides

• Triglycerides (neutral fats) are non-polar molecules composed of one glycerol molecule bonded to three fatty acids by ester bonds.
• Triglycerides function as energy storage reserves.
• Triglycerides are broken down via hydrolysis using lipases or alkaline mediums and heat.

Saponifiable Lipids: Phospholipids

• Phospholipids are important structural components of cell membranes.
• Phospholipids are amphipathic, possessing a hydrophilic head and hydrophobic tails.
• Phospholipids have a glycerol or sphingosine backbone.
• Examples include glycerophospholipids and sphingophospholipids.

Saponifiable Lipids: Glycolipids

• Glycolipids are essential for cell recognition.
• Glycolipids are found on the outer cell membrane.

Non-Saponifiable Lipids: Terpenes

• Terpenes are polymers of propene, often with cyclization at one end and a polar OH group at the other.
• Terpenes are moderately amphipathic, and examples include Vitamin A, E, K, and carotenoids.

Non-Saponifiable Lipids: Steroids

• Steroids are cyclic molecules with different functional groups, involved in communication (hormones) and other functions.
• Steroid hormones include estrogen, progesterone, testosterone, corticosterone, and adrenal hormones.
• Cholesterol is a steroid crucial for membrane fluidity.

Lipid Interactions

• Lipids' amphipathic nature results in various self-assemblies in water.
• Monolayers, bilayers, and micelles are examples of these assemblies.

Other

• Vit. D, plays a crucial role in growth and bone development (synthesized in skin).
• Cholesterol, is a structural component of plasma membranes, controlling fluidity.
• Cholesterol is a precursor for steroid hormones.

Explore the fascinating world of lipids in this quiz covering Chapter 2 on Molecular Components of Cells. Learn about the different types of lipids, their functions, and the process of saponification. Test your knowledge on phospholipids, triglycerides, and steroid hormones.